1969 Dart Swinger bench seat belt Question

Shoulder belts for 68 and later. The right officer just might write you a fine for lack of. Good luck with that. Those short rear belts are where they should be. The longer belts placed outboard could go out the door as passengers climb out. They could have pushed that anchor point farther outboard. Narrow *** kids must have been a factor. Draw them tight farther from the exterior/glass.
First seat belts in automobiles were adapted from aircraft applications. They severely lacked design engineering. Aftermarket 3 point retractable ( Wesco I think ) are a popular option to the OEM mess of separate lap and shoulder belts.